ALBERT

Description: An ecosystem approach to fisheries management requires an understanding of the impact of predatory fishes on the underlying prey resources. Defining trophic connections and measuring rates of food consumption by apex predators lays the groundwork for gaining insight into the role of predators and commercial fisheries in influencing food web structure and ecosystem dynamics.We analyzed the stomach contents of 545 common dolphinfish (Coryphaena hippurus) sampled from 74 sets of tuna purse-seine vessels fishing in the eastern Pacific Ocean (EPO) over a 22-month period. Stomach fullness of these dolphinfish and digestion state of the prey indicated that diel feeding periodicity varied by area and may be related to the digestibility and energy content of the prey. Common dolphinfish in the EPO appear to feed at night, as well as during the daytime. We analyzed prey importance by weight, numbers, and frequency of occurrence for five regions of the EPO. Prey importance varied by area. Flyingfishes, epipelagic cephalopods, tetraodontiform fishes, several mesopelagic fishes, Auxis spp., and gempylid fishes predominated in the diet. Ratios of prey length to predator length ranged from 0.014 to 0.720. Consumption-rate estimates averaged 5.6% of body weight per day. Stratified by sex, area, and length class, daily rations ranged up to 9.6% for large males and up to 19.8% for small dolphinfish in the east area (0–15°N, 111°W–coastline). Because common dolphinfish exert substantial predation pressure on several important prey groups, we concluded that their feeding ecology provides important clues to the pelagic food web and ecosystem structure in the EPO.

Description: English:Recent calls for a more holistic approach to fisheries management have motivated developmentof trophic mass-balance models of ecosystems that underlie fisheries production. We developeda model hypothesis of the pelagic ecosystem in the eastern tropical Pacific Ocean (ETP) togain insight into the relationships among the various species in the system and to explore the ecologicalimplications of alternative methods of harvesting tunas. We represented the biomasses ofand fluxes between the principal elements in the ecosystem with Ecopath, and examined theecosystem's dynamic, time-series behavior with Ecosim. We parameterized the model for 38species or groups of species, and described the sources, justifications, assumptions, and revisionsof our estimates of the various parameters, diet relations, fisheries landings, and fisheries discardsin the model. We conducted sensitivity analyses with an intermediate version of the model,for both the Ecopath mass-balance and the dynamic trajectories predicted by Ecosim. The analysisshowed that changes in the basic parameters for two components at middle trophic levels,Cephalopods and Auxis spp., exert the greatest influence on the system. When the CephalopodQ/B and Auxis spp. P/B were altered from their initial values and the model was rebalanced, thetrends of the biomass trajectories predicted by Ecosim were not sensitive, but the scaling was sensitivefor several components. We described the review process the model was subjected to, whichincluded reviews by the IATTC Purse-seine Bycatch Working Group and by a working group supportedby the National Center for Ecological Analysis and Synthesis. We fitted the model to historicaltime series of catches per unit of effort and mortality rates for yellowfin and bigeye tunasin simulations that incorporated historical fishing effort and a climate driver to represent theeffect of El Niño-Southern Oscillation-scale variation on the system. The model was designed toevaluate the possible ecological implications of fishing for tunas in various ways. We recognizethat a model cannot possibly represent all the complexity of a pelagic ocean ecosystem, but webelieve that the ETP model provides insight into the structure and function of the pelagic ETP.Spanish:Llamamientos recientes hacia un enfoque más holístico al ordenamiento de la pesca hanmotivado el desarrollo de modelos tróficos de balance de masas de los ecosistemas que sostienenla producción pesquera. Desarrollamos una hipótesis modelo del ecosistema pelágico en el OcéanoPacífico oriental tropical (POT) con miras a mejorar los conocimientos de las relaciones entre lasdistintas especies en el sistema y explorar las implicaciones ecológicas de métodos alternativos decapturar atunes. Con Ecopath representamos las biomasas de los elementos principales en el ecosistema,y los flujos entre los mismos, y con Ecosim examinamos el comportamiento dinámico delecosistema con el tiempo. Parametrizamos el modelo para 38 especies o grupos de especies(denominados “componentes” del modelo), y describimos las fuentes, justificaciones, supuestos, yrevisiones de nuestras estimaciones de los distintos parámetros, relaciones basadas en dieta, capturasretenidas de las pesquerías, y descartes de las mismas en el modelo. Realizamos análisis desensibilidad con una versión intermedia del modelo, para el balance de masas de Ecopath y lastrayectorias dinámicas predichas por Ecosim también. El análisis demostró que cambios en losparámetros básicos para dos componentes en niveles tróficos medianos, Cefalópodos y Auxis spp.,ejercieron la mayor influencia sobre el sistema. Cuando se alteraron el Q/B de los Cefalópodos yel P/B de los Auxis spp. de sus valores iniciales y se balanceó el modelo de nuevo, las tendenciasde las trayectorias de la biomasa predichas por Ecosim no fueron sensibles, pero la escala fue sensiblepara varios componentes. Describimos el proceso de revisión al que fue sujeto el modelo,inclusive revisiones por el Grupo de Trabajo sobre Captura Incidental de la CIAT y un grupo detrabajo apoyado por el Centro Nacional para Síntesis y Análisis Ecológicos. Ajustamos el modeloa series de tiempo históricas de capturas por unidad de esfuerzo y tasas de mortalidad de atunesaleta amarilla y patudo en simulaciones que incorporaron esfuerzo de pesca histórico e impulsosclimáticos para representar el efecto de variaciones a escala de El Niño-Oscilación del Sur sobreel sistema. El modelo fue diseñado para evaluar las posibles implicaciones ecológicas de la pescaatunera de varias formas. Reconocemos la imposibilidad de que el modelo represente toda la complejidadde un ecosistema oceánico pelágico, pero creemos que el modelo del POT mejora losconocimientos de la estructura y función del POT pelágico.

Description: This article is bilingual and contains both English and Spanish translations.

Description: In this study we describe the courtship and spawning behaviors of captive yellowfin tuna (Thunnus albacares), their spawning periodicity, the influence of physical and biological factors on spawning and hatching, and egg and early-larval development of this species at the Achotines Laboratory, Republic of Panama, during October 1996 through March 2000. Spawning occurred almost daily over extended periods and at water temperatures from 23.3° to 29.7°C. Water temperature appeared to be the main exogenous factor controlling the occurrence and timing of spawning. Courtship and spawning behaviors were ritualized and consistent among three groups of broodstock over 3.5 years. For any date, the time of day of spawning (range: 1330 to 2130 h) was predictable from mean daily water temperature, and 95% of hatching occurred the next day between 1500 and 1900 h. We estimated that females at first spawning averaged 1.6−2.0 years of age. Over short time periods (〈1 month), spawning females increased their egg production from 30% to 234% in response to shortterm increases in daily food ration of 9% to 33%. Egg diameter, notochord length (NL) at hatching, NL at first feeding, and dry weights of these stages were estimated. Water temperature was significantly, inversely related to egg size, egg-stage duration, larval size at hatching, and yolksac larval duration.

Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography 60 (2015): 2059–2078, doi:10.1002/lno.10155.

Description: Transitions between life cycle stages by the harmful dinoflagellate Alexandrium fundyense are critical for the initiation and termination of its blooms. To quantify these transitions in a single population, an Imaging FlowCytobot (IFCB), was deployed in Salt Pond (Eastham, Massachusetts), a small, tidally flushed kettle pond that hosts near annual, localized A. fundyense blooms. Machine-based image classifiers differentiating A. fundyense life cycle stages were developed and results were compared to manually corrected IFCB samples, manual microscopy-based estimates of A. fundyense abundance, previously published data describing prevalence of the parasite Amoebophrya, and a continuous culture of A. fundyense infected with Amoebophrya. In Salt Pond, a development phase of sustained vegetative division lasted approximately 3 weeks and was followed by a rapid and near complete conversion to small, gamete cells. The gametic period (∼3 d) coincided with a spike in the frequency of fusing gametes (up to 5% of A. fundyense images) and was followed by a zygotic phase (∼4 d) during which cell sizes returned to their normal range but cell division and diel vertical migration ceased. Cell division during bloom development was strongly phased, enabling estimation of daily rates of division, which were more than twice those predicted from batch cultures grown at similar temperatures in replete medium. Data from the Salt Pond deployment provide the first continuous record of an A. fundyense population through its complete bloom cycle and demonstrate growth and sexual induction rates much higher than are typically observed in culture.

Description: National Science Foundation Grant Number: OCE-0430724, OCE-0911031, and OCE-1314642; National Institutes of Health Grant Number: NIEHS-1P50-ES021923-01; National Park Service (NPS) Cooperative Agreement Grant Number: H238015504; Gordon and Betty Moore Foundation Grant Number: #2649 to HMS; IOF Grant Number: MOHAB PIOF-GA-252260

Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography: Methods 15 (2017): 94–102, doi:10.1002/lom3.10145.

Description: Recent advances in plankton ecology have brought to light the importance of variability within populations and have suggested that cell-to-cell differences may influence ecosystem-level processes such as species succession and bloom dynamics. Flow cytometric cell sorting has been used to capture individual plankton cells from natural water samples to investigate variability at the single cell level, but the crude taxonomic resolution afforded by the fluorescence and light scattering measurements of conventional flow cytometers necessitates sorting and analyzing many cells that may not be of interest. Addition of imaging to flow cytometry improves classification capability considerably: Imaging FlowCytobot, which has been deployed at the Martha's Vineyard Coastal Observatory since 2006, allows classification of many kinds of nano- and microplankton to the genus or even species level. We present in this paper a modified bench-top Imaging FlowCytobot (IFCB-Sorter) with the capability to sort both single cells and colonies of phytoplankton and microzooplankton from seawater samples. The cells (or subsets selected based on their images) can then be cultured for further manipulation or processed for analyses such as nucleic acid sequencing. The sorting is carried out in two steps: a fluorescence signal triggers imaging and diversion of the sample flow into a commercially available “catcher tube,” and then a solenoid-based flow control system isolates each sorted cell along with 20 μL of fluid.

Description: NSF Grant Number: OCE-11300140; WHOI internal support; NSERC through a Post-Graduate Masters award

Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 13 (2018): e0207532, doi:10.1371/journal.pone.0207532.

Description: Acoustic standing waves can precisely focus flowing particles or cells into tightly positioned streams for interrogation or downstream separations. The efficiency of an acoustic standing wave device is dependent upon operating at a resonance frequency. Small changes in a system’s temperature and sample salinity can shift the device’s resonance condition, leading to poor focusing. Practical implementation of an acoustic standing wave system requires an automated resonance control system to adjust the standing wave frequency in response to environmental changes. Here we have developed a rigorous approach for quantifying the optimal acoustic focusing frequency at any given environmental condition. We have demonstrated our approach across a wide range of temperature and salinity conditions to provide a robust characterization of how the optimal acoustic focusing resonance frequency shifts across these conditions. To generalize these results, two microfluidic bulk acoustic standing wave systems (a steel capillary and an etched silicon wafer) were examined. Models of these temperature and salinity effects suggest that it is the speed of sound within the liquid sample that dominates the resonance frequency shift. Using these results, a simple reference table can be generated to predict the optimal resonance condition as a function of temperature and salinity. Additionally, we show that there is a local impedance minimum associated with the optimal system resonance. The integration of the environmental results for coarse frequency tuning followed by a local impedance characterization for fine frequency adjustments, yields a highly accurate method of resonance control. Such an approach works across a wide range of environmental conditions, is easy to automate, and could have a significant impact across a wide range of microfluidic acoustic standing wave systems.

Description: This research was supported by grants from the National Institute of General Medical Sciences of the National Institutes of Health under award number R21GM107805 and the NSF under award number (OCE-1130140 and OCE-1131134) to SWG, RJO, and HMS.

Description: © The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Evolutionary Biology 12 (2012): 209, doi:10.1186/1471-2148-12-209.

Description: Marine phytoplankton drift passively with currents, have high dispersal potentials and can be comprised of morphologically cryptic species. To examine molecular subdivision in the marine diatom Thalassiosira rotula, variations in rDNA sequence, genome size, and growth rate were examined among isolates collected from the Atlantic and Pacific Ocean basins. Analyses of rDNA included T. gravida because morphological studies have argued that T. rotula and T. gravida are conspecific. Culture collection isolates of T. gravida and T. rotula diverged by 7.0 ± 0.3% at the ITS1 and by 0.8 ± 0.03% at the 28S. Within T. rotula, field and culture collection isolates were subdivided into three lineages that diverged by 0.6 ± 0.3% at the ITS1 and 0% at the 28S. The predicted ITS1 secondary structure revealed no compensatory base pair changes among lineages. Differences in genome size were observed among isolates, but were not correlated with ITS1 lineages. Maximum acclimated growth rates of isolates revealed genotype by environment effects, but these were also not correlated with ITS1 lineages. In contrast, intra-individual variation in the multi-copy ITS1 revealed no evidence of recombination amongst lineages, and molecular clock estimates indicated that lineages diverged 0.68 Mya. The three lineages exhibited different geographic distributions and, with one exception, each field sample was dominated by a single lineage. The degree of inter- and intra-specific divergence between T. gravida and T. rotula suggests they should continue to be treated as separate species. The phylogenetic distinction of the three closely-related T. rotula lineages was unclear. On the one hand, the lineages showed no physiological differences, no consistent genome size differences and no significant changes in the ITS1 secondary structure, suggesting there are no barriers to interbreeding among lineages. In contrast, analysis of intra-individual variation in the multicopy ITS1 as well as molecular clock estimates of divergence suggest these lineages have not interbred for significant periods of time. Given the current data, these lineages should be considered a single species. Furthermore, these T. rotula lineages may be ecologically relevant, given their differential abundance over large spatial scales.

Description: This research was supported by National Science Foundation grants, NSF 0727227 (to TAR) and NSF SBE0245039 (to URI, TAR). Part of the research was conducted using instrumentation supported by NSF-EPSCoR grants 0554548 and 1004057.

Description: Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 57 (2012): 1572-1578, doi:10.4319/lo.2012.57.5.1572.

Description: We used a time-lapse imaging approach to examine cell division in the marine centric diatom Ditylum brightwellii and observed that daughter cells who inherited their parents' hypothecal frustule half were more likely to divide before their sisters. This is consistent with observations in Escherichia coli of a bias between sister cells, where faster growth in one sister is thought to arise from its inheriting parental material with less oxidative damage. We also observed that hypothecal sisters in D. brightwellii were more likely to inherit a greater proportion of their parents' cellular material, similar to what has been seen in E. coli. We found a statistically significant correlation between the amount of parental material inherited by a hypothecal daughter and its relative division rate, indicating that this extra material inherited by the hypothecal daughter plays a role in its more rapid division. Furthermore, the intercept in this regression was greater than zero, indicating that other factors, such as differences in the quality of inherited material, also play a role. This similarity between two taxonomically distant microbes suggests that favoritism toward one daughter might occur broadly among unicellular organisms that reproduce asexually by binary fission. Such a bias in cell division might be advantageous, given model predictions that show that favoring one daughter at the expense of the other can result in higher population growth rates, increasing the chance that a cell's genotype will survive compared to a model where the daughters divide at equal rates.

Description: This research was funded in part by the Woods Hole Oceanographic Institution through an Ocean Life Institute Postdoctoral Scholarship to S.R.L. and by support to R.J.O. and H.M.S. from the Gordon and Betty Moore Foundation.

Description: Author Posting. © National Academy of Sciences, 2020. This article is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 117(22), (2020): 12215-12221, doi: 10.1073/pnas.1918439117.

Description: Picophytoplankton are the most abundant primary producers in the ocean. Knowledge of their community dynamics is key to understanding their role in marine food webs and global biogeochemical cycles. To this end, we analyzed a 16-y time series of observations of a phytoplankton community at a nearshore site on the Northeast US Shelf. We used a size-structured population model to estimate in situ division rates for the picoeukaryote assemblage and compared the dynamics with those of the picocyanobacteria Synechococcus at the same location. We found that the picoeukaryotes divide at roughly twice the rate of the more abundant Synechococcus and are subject to greater loss rates (likely from viral lysis and zooplankton grazing). We describe the dynamics of these groups across short and long timescales and conclude that, despite their taxonomic differences, their populations respond similarly to changes in the biotic and abiotic environment. Both groups appear to be temperature limited in the spring and light limited in the fall and to experience greater mortality during the day than at night. Compared with Synechococcus, the picoeukaryotes are subject to greater top-down control and contribute more to the region’s primary productivity than their standing stocks suggest.

Description: We thank E. T. Crockford, E. E. Peacock, J. Fredericks, Z. Sandwith, the MVCO Operations Team, and divers of the Woods Hole Oceanographic Institution diving program. This work was supported by NSF Grants OCE-0119915 (to R.J.O. and H.M.S.) and OCE-1655686 (to M.G.N., R.J.O., A.R.S., and H.M.O.); NASA Grants NNX11AF07G (to H.M.S.) and NNX13AC98G (to H.M.S.); Gordon and Betty Moore Foundation Grant GGA#934 (to H.M.S.); and Simons Foundation Grant 561126 (to H.M.S.).

Description: 2020-11-15

Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Marine Ecology Progress Series 550 (2016): 65-81, doi:10.3354/meps11687.

Description: Protozoa play important roles in grazing and nutrient recycling, but quantifying these roles has been hindered by difficulties in collecting, culturing, and observing these often-delicate cells. During long-term deployments at the Martha’s Vineyard Coastal Observatory (Massachusetts, USA), Imaging FlowCytobot (IFCB) has been shown to be useful for studying live cells in situ without the need to culture or preserve. IFCB records images of cells with chlorophyll fluorescence above a trigger threshold, so to date taxonomically resolved analysis of protozoa has presumably been limited to mixotrophs and herbivores which have eaten recently. To overcome this limitation, we have coupled a broad-application ‘live cell’ fluorescent stain with a modified IFCB so that protozoa which do not contain chlorophyll (such as consumers of unpigmented bacteria and other heterotrophs) can also be recorded. Staining IFCB (IFCB-S) revealed higher abundances of grazers than the original IFCB, as well as some cell types not previously detected. Feeding habits of certain morphotypes could be inferred from their fluorescence properties: grazers with stain fluorescence but without chlorophyll cannot be mixotrophs, but could be either starving or feeding on heterotrophs. Comparisons between cell counts for IFCB-S and manual light microscopy of Lugol’s stained samples showed consistently similar or higher counts from IFCB-S. We show how automated classification through the extraction of image features and application of a machine-learning algorithm can be used to evaluate the large high-resolution data sets collected by IFCBs; the results reveal varying seasonal patterns in abundance among groups of protists.

Description: This research was supported in part by NSF (grants OCE-1130140, OCE-1434440), NASA (grants NNX11AF07G and NNX13AC98G), the Gordon and Betty Moore Foundation (grants 934 and 2649), and the Woods Hole Oceanographic Institution’s Innovative Technology Program.